Early and late changes in the normal mouse bladder reservoir function due to irradiation and cis-DDP

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Lower urinary tract function after intra-arterial chemotherapy with concurrent pelvic radiotherapy for invasive bladder cancer

BACKGROUND

Intra-arterial chemotherapy with concurrent pelvic radiotherapy as a bladder-sparing regimen for invasive bladder cancer is highly promising for selected patients. However, lower urinary tract function after this treatment has not been fully investigated.

METHODS

The urodynamic effects of intra-arterial chemotherapy with concurrent pelvic radiotherapy were retrospectively evaluated in 14 patients with organ-confined invasive bladder cancer. The post-treatment urodynamic findings were compared with the pretreatment ones (n = 7), and a comparison was made between the serial urodynamic findings after the treatment in another seven patients who were able to undergo the pretreatment urodynamic study (UDS).

RESULTS

The median follow-up period up to the latest UDS was 34 months. Of the 14 patients, the latest UDS revealed some storage dysfunctions in 11 (79%) and some emptying dysfunctions in three (23%). Uninhibited detrusor contraction and decreased bladder compliance were recorded in 29 and 43% at the pretreatment UDS and approximately 50-60 and 20-60% in the serial follow-up studies, respectively (n = 7). Impaired detrusor contractility lasted in one patient. In the seven patients without the pretreatment UDS, decreased maximum cystometric capacity and decreased compliance were recorded in approximately 50-60 and 20-60% at the serial UDS, respectively. Detrusor contractility was aggravated in one patient and completely lost in one with time.

CONCLUSIONS

The urodynamic findings indicate that the bladder-sparing regimen might result in perpetuating the lower urinary tract dysfunctions due to invasive bladder cancer itself and/or transurethral surgery and might injure the infrasacral autonomic nerves and the bladder itself.

Radiation tolerance of normal mouse bladders after intravesical chemotherapy

The aim of this study was to compare functional damage in normal mouse bladder after various initial intravesical therapies and to investigate tolerance to subsequent irradiation. Six consecutive weekly intravesical instillations of Mitomycin C (MMC) or doxorubicin (DOX) were used as the initial therapy. Irradiation with single doses of 10-25 Gy (X-rays) was given at 4 or 12 weeks after intravesical treatment. Functional bladder damage was assessed from changes in the micturition frequency, expressed as frequency index (FI, number of urination events/ml urine in a 24-h test period) and from cystometry measurements of bladder volume at 52-56 weeks. Irradiation alone caused a temporary acute response (increased FI) within the first 4 weeks and a progressive late response starting from 15 to 37 weeks, depending on the radiation dose. A reduced bladder capacity was also evident at 52-56 weeks after 25 Gy. Intravesical MMC or DOX caused a 3-fold increase in FI during intravesical therapy with recovery to control levels within 2-3 weeks after cessation of treatment. Irradiation 4 weeks after MMC, or 4 or 12 weeks after DOX resulted in acute responses very similar to irradiation alone. There was no difference in time of onset or extent of late bladder damage when irradiation was given after DOX, compared with irradiation alone as assessed from repeated measurements of FI or cystometry at 52-56 weeks. In contrast, irradiation 12 weeks after MMC led to a decrease in acute radiation response compared with X-rays alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Late changes in the normal mouse bladder after irradiation alone or in combination with cis-DDP or cyclophosphamide, assessed by stereological analysis

Stereological analysis has been performed to investigate the late changes in the normal mouse bladder one year after radiation alone (10-25 Gy) or radiation (10-15 Gy) combined with cyclophosphamide (CTX), 100 mg/kg, or cis-diamminedichloroplatinum (II) (cis-DDP), 6 mg/kg. A significant increase in total volume of urothelium was found in the group treated with CTX combined with radiation compared with the control. The total volume of connective tissue in the muscular layer in the groups which received X-rays only showed a significant increase compared to the control. There also seemed to be an increase in the amount of connective tissue in muscular tissue, although this was not statistically significant, in the groups treated with CTX and irradiation compared with CTX alone. This indicates the importance of radiation in the development of late damage. Results from bladders treated with cis-DDP alone or combined with radiation were statistically inconclusive due to the small number of animals in each group. The group treated with CTX and radiation (15 Gy) showed a significant decrease in the total volume of lamina propria, but no difference was found in the other treatment groups when comparing connective tissue, the muscular layer or the amount of vessels and capillaries with their corresponding control groups. Stereological analysis seems a feasible method to demonstrate late bladder tissue changes encountered after irradiation alone or combined with chemotherapy.

Early and late damage in the mouse bladder after radiation combined with cyclophosphamide or cisplatinum, evaluated by two different functional assays

Early and late changes in the reservoir function of the mouse bladder were investigated after irradiation alone or combined with cisplatinum (cis-DDP) or cyclophosphamide (CTX). Bladder function was repeatedly assessed from independent assays of urination frequency and cystometry. Treatments consisted of 10-30 Gy x-rays alone or 10-22.5 Gy combined with chemotherapy (cis-DDP 6 mg/kg i.p. or CTX 100 mg/kg i.p.). Within 30 days after treatment, early damage was detected by both assays but the correlation between assays was significant only in the group treated with x-rays and CTX. The late response was irreversible and a correlation was found (p < 0.05) between urination frequency and the results of the cystometry assay in all treatment groups. After x-rays alone or x-rays plus cis-DDP, the RD50 values (the radiation dose that induced a response in 50% of the animals) decreased with time as damage occurred. After x-rays plus CTX, maximum damage appeared much earlier and RD50 values tended to increase from 12 to 40 weeks. Comparison of these RD50 values gave a dose-effect factor (the ratio between the RD50 doses for x-rays alone and x-ray plus drug) of 1.1 to 1.3 for cis-DDP in both assays. The enhancing effect of CTX on bladder reservoir function was greater, especially in the results of the frequency assay, as indicated by considerably lower RD50 values. This resulted in an estimated dose-effect factor of up to 2.4. In conclusion, both assays are suitable for investigating early and late bladder damage, although the functional defect measured is different. Both CTX and cis-DDP increased early and late bladder damage when combined with irradiation. Late damage appeared earlier in combined treatment groups than in mice treated with irradiation alone.